IntelliJ IDEA 2018.2 Help

Code completion

This section covers various techniques of context-aware code completion that allow you to speed up your coding process.

Completion also works for symbols from third-party code. In most cases all you need is to add the required files to your project, see Configuring JavaScript Libraries for details.

Basic completion: names and keywords

Basic code completion helps you complete the names of classes, methods, fields, and keywords within the visibility scope. When you invoke code completion, IntelliJ IDEA analyses the context and suggests the choices that are reachable from the current caret position (suggestions also include Live templates).

Code completion is available for custom file types. However, IntelliJ IDEA does not recognize the structure of such files, and suggests options regardless of whether they are appropriate in the current context.

If basic code completion is applied to a part of a field, parameter, or variable declaration, IntelliJ IDEA suggests a list of possible names depending on the item type.

Invoking basic code completion for the second time shows inaccessible classes and members (these can be made public by applying an intention action).

When invoked for the third time in a row, IntelliJ IDEA will look for suggestions for classes and interface names in the entire project, regardless of dependencies. If the necessary class is not yet imported, it will be imported automatically.

Invoke basic completion

Start typing a name.

Press Ctrl+Space or choose Code | Completion | Basic from the main menu.

If_necessary, press Ctrl+Space for the second time (or press Ctrl+Alt+Space).

This shows inaccessible classes and members as well as static fields and methods.

When invoked for the third time, basic code completion expands the suggestion list to all classes throughout the project, regardless of the dependencies.

Basic completion is available even when you are using a non-English keyboard layout.

Completion in the Stream API chains is aware of type casts, so the list will not only contain items based on the existing call filter(String.class::isInstance), but also automatically typecasted suggestions.

Smart completion based on type

Smart code completion filters the suggestions list and shows only the types applicable to the current context.

Smart completion is useful in situations when it is possible to determine the appropriate type:

In the right part of assignment statements

In variable initializers

In return statements

In the list of arguments of a method call

After the new keyword in an object declaration

In chained expressions

Invoke smart completion

Start typing.

Press Ctrl+Shift+Space or choose Code | Completion | SmartType from the main menu.

The most suitable suggestion for the current context is highlighted.

For chained expressions, suggestions are sorted by how frequently they are used in the project. When any of the suggested method calls takes an argument that is not yet available in the context, after you select it the IDE defines a local variable of the required type.

If necessary, press Ctrl+Shift+Space once again. This lets you complete:

Collections, lists and arrays. IntelliJ IDEA searches for symbols with the same component type and suggests converting them.

Static method calls or constant references. IntelliJ IDEA scans for static methods and fields, and suggests the ones suitable in the current context.

Completion for chained expressions is only available for Java and requires the project to be built with the IntelliJ IDEA compiler (not the Gradle compiler).

Statements completion

Statements completion enables you to create syntactically correct code constructs. It inserts the necessary syntax elements (parentheses, braces, semicolons etc.) and gets you in a position where you can start typing the next statement.

Complete a method declaration

Start typing a method declaration and press Ctrl+Shift+Enter after the opening parenthesis.

Complete a code construct

Start typing a code construct and press Ctrl+Shift+Enter. IntelliJ IDEA automatically completes the construct and adds the required punctuation, and the caret is placed at the next editing position.

Wrap a method call argument

Type an expression, for example

"test"

Type a method call. When println gets the focus in the suggestion list, select it with Ctrl+Shift+Enter:

The resulting code will look like the following:

System.out.println("test");

Hippie completion: expanding words based on context

Hippie completion is a completion engine that analyses your text in the visible scope and generates suggestions from the current context. It helps you complete any word from any of the currently opened files.

Expand a string at caret to an existing word

Press Shift+Alt+/ or choose Code | Completion | Cyclic Expand Word (Backward) to search for matching words after the caret and in other open files.

The first suggested value appears, and the prototype is highlighted in the source code.

Accept the suggestion, or hold the Alt key and keep pressing / until the desired word is found.

Postfix code completion

Postfix code completion helps you reduce backward caret jumps as you write code. It allows you to transform an already typed expression to a different one based on a postfix you type after the dot, the type of expression, and its context.

Transform a statement with a postfix

Type an expression and then type a postfix after a dot, for example .if:

publicclassFoo{voidm(booleanb){b.if}}

funfoo(x:Boolean){x.if}

The initial expression gets wrapped with an if statement:

publicclassFoo{voidm(booleanb){if(b){}}}

funfoo(x:Boolean){if(x){}}

To disable certain postfix completion templates, in the Settings/Preferences dialog (Ctrl+Alt+S) select Editor | General | Postfix Completion. You can also choose which key you want to use to expand postfix templates: Tab, Space, or Enter.

You can edit the predefined postfix templates, for example to replace a long key with a shorter one, or to expand the list of expression types it's applicable to.

Postfix completion options are shown as part of the basic completion suggestions list. To see a full list of postfix completions applicable in the current context, press Ctrl+J.

Create custom postfix templates

Specify the Key, i.e. the combination of symbols that will invoke the template, select which expression types the new template will be applicable to, and type the target expression in the following format: $EXPR$ <target_expression>, for example, $EXPR$ =!null.

Postfix code completion is similar to live templates which allow you to create custom constructs to be used anywhere inside your code.

Completion of tags and attribute names is based on the DTD or Schema the file is associated with. If there is no schema association, IntelliJ IDEA will use the file content (tag and attribute names and their values) to complete your input.

In XML/XSL and JSP/JSPX files, completion for taglibs and namespaces is available.

Complete tag names

Press < and start typing the tag name. IntelliJ IDEA displays the list of tag names appropriate in the current context. Use the ArrowUp and ArrowDown buttons to scroll through the list.

Press Enter to accept a selection from the list. If your file is associated with a schema or a DTD, IntelliJ IDEA automatically inserts the mandatory attributes according to it.

Import a taglib declaration

If you need to use tags declared in a tag library, you need to import this taglib before any custom tag from it can be used.

Configure code completion settings

Configure completion options

To automatically display the suggestions list, select the Show suggestions as you type checkbox. If the checkbox is cleared, you have to call code completion explicitly by pressing Ctrl+Space for basic completion or Ctrl+Shift+Space for smart completion.

You can also choose to automatically insert suggestions when there's just one option: select the completion type under Automatically insert single suggestions for.

To sort suggestions in the alphabetical order, instead of sorting them by relevance, select the Sort suggestions alphabetically checkbox.

You can also toggle these modes by clicking or respectively in the lower-right corner of the suggestions list.

If you want case to be taken into account when suggesting completion options, select Match case and choose whether you want to match case for first letters only, or for all letters.

If you want the documentation popup to be displayed automatically for each item in the suggestions list as you scroll it, select the Show documentation popup in option. In the field to the right, specify the delay (in milliseconds), after which the pop-up window should appear.

Exclude a class or package from completion

Under Exclude from import and completion, add the names of classes or packages that you want to exclude from completion. The classes you specify here will not appear in the suggestions list.

You can also select a completion suggestion when it appears in the editor: press Alt+Enter and select Exclude from there:

The sorting icons only appear if the list is long and are not displayed for lists containing just a few entries.

Completion tips and tricks

Narrow down the suggestions list

You can narrow down the suggestions list by typing any part of a word (even characters from somewhere in the middle), or invoking code completion after a dot separator. IntelliJ IDEA will show suggestions that include the characters you've entered in any positions.

Accept a suggestion

You can accept a suggestion from the list in one of the following ways:

Press Enter or double-click a list item to insert it to the left of the caret.

Press Tab to replace the characters to the right from the caret.

Use Ctrl+Shift+Enter to make the current code construct syntactically correct (balance parentheses, add missing braces and semicolons, etc.)

You can also use specific keys to insert the selected completion suggestion: in the Settings/Preferences dialog (Ctrl+Alt+S) choose Editor | General | Code Completion and select the Insert selected suggestion by pressing space, dot or other context-dependent keys option. These keys depend on the language, your context, etc. For Java, such keys include Space, Tab, [ and ], ( and ), and some more.

While this setting helps you save time, turning it on may result in items being inserted accidentally.

Negate an expression

You can negate an expression in Java by pressing ! after you have selected it from the suggestions list: As a result, the expression will be negated:

Negating an expression works this way if you have the Insert selected variant by typing dot, space, etc. option enabled in the Code Completion settings page, or invoke code completion explicitly, or change a selection in the suggestions list explicitly.

Completion shortcuts

You can use the following live templates shortcuts for one of the most frequently used statements:

sout: prints System.out.printIn()

soutm: adds the current class and method names

soutp: adds method parameter names and values

soutv: adds the last variable value

View reference

You can use the Quick Definition View by pressing Ctrl+Shift+I when you select an entry in the suggestions list:

View code hierarchy

You can view code hierarchy when you've selected an entry from the suggestions list:

Ctrl+H: view type hierarchy

Ctrl+Alt+H: view call hierarchy.

Ctrl+Shift+H: view method hierarchy.

Troubleshooting

If code completion doesn't work, this may be due to one of the following reasons:

The Power Save Mode is on (File | Power Save Mode). Turning it on minimizes power consumption of your laptop by eliminating the background operations, including error highlighting, on-the-fly inspections, and code completion.